This invention relates to the construction of trucks such as are used for carrying thousands of gallons of liquids and particularly to a truck in which the bed and cab of the truck are supported by a suspension system.
There is a demand for trucks that are used for carrying large quantities of liquids (in excess of 4000 gal). These liquids include water such as for transporting water to the site of a fire, fuels, water, etc.
The standard design approach to construction of trucks for these applications is illustrated in the assembly view of FIG. 1. There is shown a tank 10 poised for mounting on top of a xe2x80x9cladderxe2x80x9d frame including beams 12 and cross members 14. The ladder frame is secured by leaf springs 16 (one for each wheel) mounted on the truck front and rear axles 20.
As shown in FIG. 1, the typical tank 10 is oblong with an axis extending from the front end to the rear end of the truck bed.
This conventional arrangement shown in FIG. 1 having several inherent limitations.
One limitation is that the elongated ladder frame must have a thickness (weight of the frame) sufficiently great to prevent excessive flexion of the frame. This requirement imposes a lower limit on the weight of the pair of elongated beams constituting the ladder frame.
A second limitation is that the arrangement of the tank and motor on top of the frame on top of leaf springs on top of the axle mandates that the center of gravity of the loaded truck is at a height above the ground that the tendency of the truck to roll over becomes an important consideration in terms of safe driving practices such as speed around curves, allowable tilt when driving on road beds that are not level, etc.
A third limitation is the amount of liquid that can be pumped out of the tank when the tank is tilted on an incline or decline. When the truck is on a 25 degree slope (incline) only about 85% of the liquid can be pumped out of the tank.
A fourth limitation is the inconvenience of performing maintenance operations particularly operations requiring temporarily dismounting of the motor that is located at an elevated height on top of the frame.
A fifth limitation is the inherent characteristic that a large fraction of the truck structure, the tank, makes no contribution to the structural strength of the truck and is subject to severe flexion because of its elongated oblong shape. Because the tank makes no contribution to the strength-rigidity of the overall truck structure, the tank is normally made as light as practical. Polypropylene tanks, made from xe2x85x9cxe2x80x3 thick sheet, is often the material of choice. With such tanks, no consideration of any contribution to overall structural strength of the truck assembly is considered.
A sixth limitation is operative when applied to Military uses of the truck according to which the overall height and length and width of the truck and weight when fully loaded are all limited by the requirement that the truck be capable of being transported on an airplane, particularly the air force C130. The more weight that is required to build the truck, the less weight of liquid can be accommodated as the truckload.
A number of references in the patent literature exemplify approaches to the problems listed in the foregoing paragraphs.
For example, U.S. Pat. No. 5,630,625 to Shaw discloses two tanks mounted on a ladder frame and having tag wheels that initially support the rear end of the truck but are automatically raised when the rear tank has been emptied.
U.S. Pat. No. 4,283,066 to Brown et al discloses a tank supported partially between the parallel members of the ladder frame comprising the truck bed.
U.S. Pat. No. 4,325,560 to Hirvonen discloses a tank comprising an elongated tubular shell whose length is substantially the length of the truck bed that functions both as a container for the fluid and is sufficiently rigid to function as the supporting frame of the truck. The front and rear axles are suspended from respective ends of the tank by links (coil springs and air springs positioned between the bottom side of the tank and the axles.
U.S. Pat. No. 5,593,070 to Sreadman discloses a cylindrical fiber glass tank supported on a metal frame between the pair of elongated members forming the frame of the bed.
None of these disclosures apply the principles adapted by the present invention to overcome the limitations of the present state of the art.
It is an object of this invention to provide a vehicle for carrying bulky loads and especially fluid loads such as water, fuels, sand, etc. It is a particular object that the vehicle has fewer tendencies to tip over when carrying the load on uneven terrain such as the side of a hill or in areas where the vehicle might encounter a ditch. In achieving this object it is inherent in the construction of the invention that the loaded vehicle have a center of gravity that is lower than is the case for vehicles of similar load carrying capacity.
An advantage of this inherently limited reduction of the overall height of the vehicle is greater ease in dimensioning the vehicle so that it can be loaded onto a transport plane.
Another object is that the ratio of weight of the loaded truck to the unloaded truck be inherently substantially higher than ratios characteristic of trucks of the present state of the art.
It is contemplated that the goal of reduced weight be achieved without sacrificing strength in terms of load carrying capacity.
The design of this vehicle is characterized by minimizing bending moments that otherwise lead to at least unsafe driving conditions and, at worst, to failure of structural members.
It is a further object that the principles of the invention are adaptable to construction of a truck that is modular so as to provide convenient access to and/or replacement of the motor and/or the cab.
This invention is directed toward a transport device for carrying a load in a carrier section in which a container (e.g., a tank) is hung on a hanger structure that is supported by a plurality of vertical hydraulic cylinders. The carrier section typically has a forward and a rearward axle but, in other versions, the truck has an additional axle and pair of wheels parallel and adjacent to front and/or rear axle. The number of cylinders depends on the number of wheels, being one cylinder for each wheel.
In one embodiment, the truck comprises a pair of cylinders supported on a front axle and another pair of cylinders supported on a rear axle (with a wheel on each end of the respective axle). The lower end of each hydraulic cylinder is secured to one axle close to one of the wheels respectively. The upper ends of the cylinders support a pair of hanger members. The container is attached to and hangs below a pair of hanger members.
Each hanger member is a yoke fashioned from a panel providing that its vertical dimension is very large compared to its horizontal dimension (thickness of the panel) and is therefore very favorable for resisting vertical flexion. Furthermore, the load. Hanging from the panel exerts a tensile load parallel to the surface of each panel so that there is no tendency for the panel to buckle.
The construction of the yoke therefore provides that a substantially reduced amount of material is required compared to construction of the prior art in which a heavy pair of beams is positioned under the load
In one embodiment, the container is a cylindrical tank with a horizontal axis vertical to the direction of travel. Each yoke is one of a pair of vertical panels (one at each end of the cylindrical tank) cut out to form the pair of yokes that straddle the cylindrical tank. Each yoke is welded near one end of the tank opposite the other yoke at the other end of the cylindrical tank. A pair of baffles is welded to the inside of the tank. Each baffle is coplanar with the yoke outside the tank. Each yoke and baffle constitute a beam having a width comparable to the diameter of the tank. Resistance to bending (flexion) of the beam is thereby optimized. Each baffle has openings that permit free flow back and forth of the fluid inside the tank.
The rear end of the carrier section has a cantilever that extends away from the carrier section and supports the engine. The engine includes the transmission coupled to the motor coupled to the radiator. The cantilever for the engine includes a pair of horizontal beams, each having one end abuttedly attached to the rear axle and the other end secured to one end of one of a pair of oblique members whose other end is secured to the nearest end of one of the yokes. The other oblique member is similarly attached to the other horizontal beam and other yoke. A pair of vertical hangers are suspended from the forward end of the yokes and have lower ends secured to the transmission to provide additional strength to supporting the engine. This arrangement provides that most of the weight of the engine is transferred as a tensile force to the oblique members and the vertical hangers. Since the force on these members is tensile, the total weight of the structure supporting the engine (the cantilever) is much smaller than constructions of the standard art where the engine is supported on top of a pair of beams.
The cab section is a unitary form module that is fastened onto the front end of the carrier section
In another version, a cantilever support is positioned on the front end of the carrier section for carrying the cab module. Containing the operators and truck crew.
In another embodiment of the invention, the carrier section has no cantilever sections for carrying a cab or engine but instead has a tongue extending in the forward direction from one axle. The free end of the tongue is attachable to a motorized vehicle.
The primary links connecting the motor, cab and tanks to the yokes are all under tensile stress so that there are no bending moments that would tend to buckle the links subject to the weight of the engine and tanks. This feature provides that the links be lighter than would be required if the links were subject to compressive force.
The primary compressive forces are exerted by the vertical hydraulic cylinders. Location of the lower ends of the cylinders secured to the axles close to the wheels ensures that there are generated no bending moments that would require extra material (greater weight for adequate strength.
Hydraulic pressure is maintained by a pump that distributes hydraulic fluid through a valve block to each of the cylinders. Hydraulic fluid pressure through the branches of the valve block to the respective cylinder is computer controlled to respond to measure of pressure by sensors, one sensor measuring pressure in a respective cylinder. The sensors respond to adverse driving conditions such as tilting on high crown uneven terrain and adjust hydraulic pressure accordingly.
A baffle-scoop under the rear end of the truck and sides of the hood reverse direction of flow of cooling air flowing rearward under the truck (as the truck moves) so that the air finally flows in the forward direction and cools the engine, then through a radiator and out through louvers on top of the engine hood. A radiator fan for increasing air flow is provided that is temperature controlled to turn on when the flow of air is insufficient to maintain the required operating temperature such as when the truck is not moving.
The foregoing summary has highlighted features, aspects and advantages of the present invention. The invention is further explained by the following description of what I presently believe to be the best mode for carrying out the invention illustrated by drawings to which are appended claims which define the scope of the invention.